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9 comments:

Deviation in Soviet measurements is the radius of the oval that 50% of the shots fall into. Some other countries used diameter in their measurements, so readers should be careful about comparing data between sources. The French used a particularly stupid measurement where they added the horizontal and vertical measures together to yield an accuracy figure ...

I believe that these are figures for a fixed gun firing at a known-range target, so no alignment or operator errors.

For real-world accuracy, I recently found the British evaluation of a captured M13/40. They wrote that the elevation gear for the gun was very coarse (not enough teeth), so achieving a precise elevation was nearly impossible. This didn't matter much at short range, but would have had terrible effects on accuracy at longer ranges, especially given the relatively low velocity of the 47/32. Just another example of you "the little things" can completely throw off evaluations based on proving ground results.

The way the British and US found the deviation is to use a fixed gun which would fire at a known target at a known range. Then draw in the center of the spread of hits afterwards. So deviation is the average from that point. Thus the targeting or sighting is irrelevant and does not affect the outcome.

That's how small arms are benchmarked too so nothing new there. You're investigating the inherent mechanical ballistics of the thing, not the whole added shebang that comes with sights and end-users and whatever else.(That's a different set of tests.)